# Why are my rollups on NotionApps showing zero (0) value or an incorrect value?

## Reason #1

When rollups are used with `average, min, max, sum` and other such calculations, Notion does not return the correct value of these rollups to NotionApps. 

In these cases, we suggest using a Formula instead of a Rollup. You can re-create `average`, `min`, `max`, and `sum` calculations with formulas. 

For example, to calculate the average number of days each Project's Tasks  take, you could create a formula like so:

```
sum(prop("Tasks").map(current.Days))/prop("Tasks").length()
```

To calculate the minimum number of days each Project's Tasks take, you could create a formula like so:

```
min(prop("Tasks").map(current.Days))
```

## Reason #2

Another common reason for incorrect Rollup or Formula data is because NotionApps does not have access to all the databases involved in the calculations.

#### **Example Scenario**

Suppose you have two databases:

* Projects
* Tasks

You’ve set up a Formula property in the Projects database (for example, “# of tasks completed”) that counts how many tasks in the Tasks database have a “Completed” status.

If NotionApps only has access to the Projects database (but not the Tasks database), Notion will return a value of 0 for the formula, even if there are completed tasks. This happens because NotionApps doesn’t have permission to read the relevant data from Tasks.<br>

#### **How to Fix**

To ensure accurate data for Rollup and Formula properties:

1. **Grant NotionApps access to all related databases.**

   Make sure NotionApps is authorized to access **every** database referenced by your Rollup or Formula properties (if you'd like to use those properties in the app).
2. **How to update database access:**
   * Go to your **Account Settings** and click on **Manage Databases**

     OR
   * Open your app builder in NotionApps, visit the **Databases** tab, and click on **Manage Databases**
3. Select the related databases.

After updating access, click on the **Reload Data** button in your app builder. NotionApps will be able to fetch the correct values for all your Rollup and Formula properties.

If you have any questions, please reach out to us at <help@notionapps.com>.&#x20;